1. Field of the Invention
The present invention relates to an abnormality determination and estimation method and an abnormality determination and estimation device for products of plastic working. More particularly, the present invention relates to an abnormality determination and estimation method and an abnormality determination and estimation device that estimate discrimination of abnormalities based on an elastic wave generated in a plastic working process.
2. Description of the Related Art
Generally, a technique has been known that uses an AE sensor for detecting an elastic wave generated when a local deformation or destruction occurs prior to entire destruction of a structure so as to monitor the structure and/or predict the destruction of the structure. This technique is used for nondestructive inspection. Thus, the present invention employs this AE sensor in a plastic working apparatus and detects the elastic wave generated in the structure in the plastic working apparatus by means of the AE sensor and estimates the detected elastic wave with respect to an elastic wave in a case of forming a non-defective product. This estimates the presence of an abnormality of the parts formed by plastic working, and determines the abnormality.
However, in a case where a determination value for estimating an abnormality, which is used for comparing a defective product and a nondefective product, is set in such a manner that the comparison is done based on the magnitude of the amplitude of the elastic wave thus detected, it is difficult to determine the difference from the characteristic value because the amplitude of the elastic wave generated when a die hits something in the plastic working process is large. This may result in a wrong determination.
Therefore, the present invention was made considering the above drawback and aims to provide an abnormality determination and estimation method and an abnormality determination and estimation device for products of plastic working to improve the precision of detection of abnormalities and discriminate the abnormalities by estimating an elastic wave for each processing step.